This invention relates to agricultural dispensing mechanisms for dispensing agricultural particulate material, and to agricultural implements incorporating such dispensing mechanisms for delivering to the ground agricultural particulate materials such as seeds, fertilizers, herbicides, insecticides, nematicides, fungicides, slug pellets and other pesticides. Examples of such implements are seed drills, seed and fertilizer drills, fertilizer dispensers for precision rowcrop planters such as planters for maize, soya beans, potatoes etc., spreaders and applicators for agricultural particulate materials, and rotary cultivators adapted to plant row crops.
In British Pat. No. 1,525,566 there is disclosed a mechanism for dispensing particulate material comprising a resilient dispensing roller. This mechanism has many practical advantages, but a problem which arises with all such dispensing mechanisms having axially fixed dispensing rollers is that of dispensing particulate material at the very slow rate which are required when sowing certain seeds. In the case of kale, for example, an application rate of 3 to 4 kilogrammes per hectare is commonly used whereas when sowing barley and other cereals, application rates between 150 and 200 kilogrammes per hectare are commonplace.
It will therefore be appreciated that an enormous variation in the rate of driving the dispensing mechanism would be needed if that were the only method of changing the rate of dispensing material.
Although the gearbox described in British Pat. No. 1,496,682 is capable of providing such variations in driving rate, this in itself is not a complete answer to the problem since, when a dispensing roller is rotated very slowly, it will be obvious (by analogy with high-fidelity records and tapes) that its dispensing accuracy and regularity (or fidelity) will suffer somewhat.
A general object of the present invention is to provide means for avoiding the need to rotate a seed or fertilizer dispensing roller unduly slowly when dispensing material at a very slow rate, while retaining the facility to dispense material at a relatively high rate when desired. A further object is to enable the change-over from high to low rate to be made quickly and easily and without the use of expensive equipment. Other objects include the provision of effective means to seal a slow rate band on a dispensing roller against lateral escape of seed, and the provision of facility to dispense seeds or other material at a slow rate either out of the main seed hopper wihtout employing a special seed bottle (or other secondary container) in the main hopper, or with such a seed bottle in the main hopper.